


Principles of Causality

by spookyknight



Category: Doctor Who (2005)
Genre: F/M
Language: English
Status: Completed
Published: 2013-09-03
Updated: 2013-09-03
Packaged: 2017-12-25 11:56:15
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,512
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/952783
Author URL: https://archiveofourown.org/users/spookyknight/pseuds/spookyknight
Summary: <blockquote class="userstuff">
              <p>The only way to ensure an outcome is to be the cause of it. The metacrisis Doctor makes his own fate with Rose Tyler in a parallel world.</p>
            </blockquote>





	Principles of Causality

**Author's Note:**

> Fulfills “Against All Odds” for trope bingo

It was bound to happen eventually. Earth was a small place, London even smaller, and with the baby TARDIS only having a small window of space and time for her playground, the odds were actually surprisingly high he’d run into Rose Tyler.

He’d slipped away this morning and taken the ship on a little trip backwards, just to give her a bit of exercise. The more practice their TARDIS got in these early stages, the faster she’d be ready for longer trips. The console was still incomplete, missing a few components thanks to the limited atmosphere and chemical composition of Earth, so today his errand was scouting for alien tech that could be useful.

Alien parts were a funny little aspect of material culture, little gizmos and miscellany that didn’t seem to fulfill any discernable purpose and therefore no one knew what to do with. Often assumed to be relics of a bygone era, unsuccessful attempts at new inventions, or even the imaginative craftings of children, objects of alien origin usually ended up as odds and ends at antique stores and jumble sales. In Pete’s World, with very little connection to the rest of the galaxy, the Doctor had quickly learned to find and make do with whatever space junk happened to fall to Earth.

As the Doctor rummaged through the stalls of the Antiques Market at the top of Portobello Road, he found he wasn’t the only one who had discovered this link between alien gadgets and second-hand goods. Through a small crowd of tourists and day trippers, Rose caught sight of him.

She was completely still, frozen in place on the pavement. Her face was pale and her eyes held the tumultuous mix of hope, fear, and despair. He hated it. The Doctor acted on instinct, moving towards her with a few halting steps, ready to comfort or support, whatever she needed from him.

“Rose?”

Hearing her name seemed to break something within her. Rose choked out a sob, tears welling in her eyes and spilling over as her hand flew up to cover her mouth. She shook her head in disbelief, her mouth trying and failing to form one word she hadn’t dared to speak in over a year.

“Doctor?”

He didn’t respond but the recognition in his face must have given him away. Rose ran to him at full speed, launching herself into his arms and crying her immense relief into his shoulder. Holding her trembling body, his mind finally caught up with what was happening. This wasn’t his Rose, he’d run into her past self, before the Crucible and the metacrisis.

Still, Rose was Rose, and the Doctor was quickly immersed in her warmth and scent. His mind could sort out the differences in their timelines, but his body knew no difference. He was always rendered rather helpless at seeing her cry, and without really thinking he nuzzled his face into her neck, placing a tender kiss below her ear. Her breath hitched suddenly, and he realized he’d crossed the line into being a bit too intimate. Rather than pull away, though, Rose simply squeezed him tighter, burrowing into his chest.

“You found me,” she whispered, almost too soft to hear.

The Doctor pulled away, then, afraid she’d pick up on his singular heartbeat now that the hysteria had passed. He detangled their embrace but kept a comforting hold on her shoulders. Rose looked up at him, eyes wet and face still shining with tear tracks but smiling brilliantly. This was going to kill him, bringing her down. It was going to tear his heart into shreds until there was nothing left.

“I will,” he said seriously. “Or, you will, actually. But not today.”

“What?” she cried, her face falling from joy into panic. “I just found you! Why—”

“Rose,” he began, her name an anchor to the emotions clouding the air between them. His tongue sneaked out to wet suddenly dry lips, thoughts racing without settling on one direction. “I’m not…”

“You’re from the future,” she supplied, letting him off the hook momentarily. It was a statement, really, with only a slight hesitancy that almost crossed over the line into the realm of a question. He held her stare, nodding just vaguely, letting her draw her own conclusion again. Rose drew a deep breath and pressed on. “And… you’re with me?”

His breath caught and he felt suddenly the full weight of this chance interaction. In this moment, he cursed his limitations. A Time Lord would be able to analyze the timelines instantly to determine the correct course of action, whether his next words would threaten the future or ensure it. But after the metacrisis, the Doctor was only partly that man, catching only glimpses of the future ahead and not the detailed map he used to access, once upon a time.

And yet, in some ways his new constraints gave him freedom. If he couldn’t connect to the timeline, he didn’t have a responsibility to it either. He also had to consider that this was Rose. He’d vowed when they left that godforsaken beach for the last time that he would never lie to her again. If he could give her a shred of hope to hold onto, a little bit of light to lead this Rose in becoming  _his_  Rose, he was going to do it.

“Yes.”

A simple affirmation, it was all he really had to offer her.

Rose nodded. “Okay.”

She smiled and he smiled back, stupid, happy, matching grins that made her chuckle at the absurdity of this meeting.

The Doctor raised a hand to her cheek, tucking a stray lock of hair from her face. He sighed heavily, closing his eyes for some modicum of control over his emotions, and leaned down until their foreheads touched together gently.

“You’re going to be brilliant, Rose. Everything you’re doing now, it’s going to work, I promise. And we’ll be together again… one day.” He opened his eyes, hardly able to see her this close but willing her to believe his words. “I’m sorry you have to wait.”

Rose bit her lip adorably, trying to fight another grin at the intimate contact between them. She pulled away slightly only to tilt her head, angling her face to better capture his lips in one impulsive move. The Doctor stiffened at first, startled by the sudden contact, but quickly melted into the gorgeously familiar sensation of snogging Rose.

She was hesitant at his initial reaction, second guessing her actions, and gasped in delighted surprise when he opened his mouth to hers, kissing her more deeply. It was more than she could have ever hoped. He kept the contact light, allowing the tantalizing slide of lips and tongue together and one hand on her neck gently tilting her head  _just so_. The Doctor didn’t seem to want anything more, so Rose didn’t push him. She was overwhelmed enough that he was returning her kiss.

They both jolted and tensed as the comm on her hip buzzed to life and Mickey’s voice came in over the static.  _“_ _Rose, where are you? We’ve got a 43 Periwinkle Alpha situation, here. It’s all hands on deck.”_

She pulled away, ducking her head sheepishly and avoiding his eyes. “That’s me…”

“Go,” he instructed softly. He took her hand in his, giving it a good squeeze before letting it go. “I  _will_  see you again, Rose Tyler.”

She smiled brightly. “Not if I see you first.”

 

* * *

 

She hadn’t seen him that morning. She was called in to Torchwood (bloody consulting) for an emergency early and didn’t have the heart to wake him, sleeping soundly and adorably as he was. By the time she arrived back at the flat he and the TARDIS were already gone on another test run, a sweet note on the counter assuring her all was well.

It’s not until he exits the newly materialized time ship that she takes him in… dark blue trousers, black printed t-shirt, and matching blue blazer… and realizes today was that day.

She’s known for a long time, but it became real the day he bought the shirt. They found it in the gift shop of a museum they visited on their travels, a ‘little shop’ full of science-related items. She remembers his excitement as he scooped the fabric up and held it taut to show her the design, recalls nearly every word of his lecture on the chemical formula — a particular compound found in bananas — printed on its face.

_“It’s the chlorophyll breakdown, Rose! It causes fluorescence that makes bananas glow blue under ultraviolet light.”_

The shirt, as demonstrated by the display, also glowed blue under blacklight. The Doctor had to have it. Since that day, she’d remained aware of its existence, folded up with other casual clothing in the middle dresser drawer. That stupid shirt was always in the back of her mind, knowing eventually this day would come.

Rose greets him with her usual embrace and welcoming snog, genuinely happy to have him home again. He lingers, clinging to her desperately, and she knows. Neither of them want to say, they don’t want to drag up the past anymore, but underneath their daily happy reunion there’s something darker today.

She excuses herself, mainly to gather her emotions back together, and retreats to the kitchen to start on dinner. Of course the Doctor wants to help, he always does, so she simply divides their tasks quietly, focusing entirely too intently on mincing vegetables. The blazer’s gone but the damn shirt remains. Rose wonders if cut onion is enough of an excuse for the tears in her eyes.

“It’s your fault,” she blurts out suddenly.

It’s entirely the wrong thing to say and not the sentiment she wants to express at all. He looks hurt, and she stops what she’s doing completely so she can shift her attention to repairing the damage. Serious conversations shouldn’t take place when one party has a knife in their hand.

“What I mean is, you made this happen. All of this,” she opens her arms, indicating everything around them. “It’s all because of you.”

“No.” The Doctor shakes his head, regarding her seriously. “It was you, Rose. You found me.”

She sighs heavily. He’s missing the point. Rose tries again. “I always remembered that day. Running into you against all odds on the street. Held onto it to get me through the hard times.”

“Rose…”

He moves towards her slowly, offering comfort, but she holds a hand up in a silent request to let her finish, to let her get through this.

“I was going to give up. The Dimension Cannon was missing…  _damn_ , everything. It was just cobbled together junk and nothing was working. But I saw you there; I felt that it was really you.” She pauses, a delicate blush rising on her cheeks as she ducks her head shyly just like that day. “I got the strength to keep going. I found the parts I needed, and we did it. We got it to work.”

“You did it,” the Doctor asserts firmly. “And you were amazing.”

She nods absently, tears welling in her eyes. “But part of me knew, when you came out of the TARDIS all smiling eyes, blue suit and no tie… part of me knew before we even left the Crucible what was going to happen.”

His face falls a little bit, and she hates herself for it, for bringing up what’s been done, what they can’t change. But this has been haunting her since that breathless, impossible moment on Portobello Road, and she has to get it out.

“And it’s not that I don’t want you, I do,” she says quickly, rushing to get the words out. “I’m glad it was you. I’m glad you’re the one who gave me the strength to keep going, so we could be together now.”

He reaches out to her and she accepts his embrace this time, falling into his arms all at once as he gathers her up effortlessly. The Doctor places a soothing kiss to her forehead, and she takes a shaky breath.

“It’s just…” She swallows, her throat gone dry. “I still hate to think he’s out there somewhere, all alone.”

“He has someone, Rose,” he assures her quietly. “Not you, and I’m sorry for that, because you’re the best.” She chuckles a bit and manages a watery smile. He squeezes her just a little tighter. “Of course you are. But  _someone_.” The Doctor pulls back to look at her. “Better with two; you’re the one who taught me that.”

She scoffs, shaking her head. “I think you knew that before you met me.”

“I knew,” he agrees dubiously. “But you’re the one who really  _taught_  me.”

“I love you. I hope you know that.” Rose looks at him pointedly, willing him to understand. “All of you.”

“Yes, I know,” he tells her quietly. “And I’m not sure what we did to deserve that, all of us. But I’m glad. And you should know… we love you, too.”

The Doctor wants her to know that, needs her to believe with all of his being that his love for her wasn’t just a side effect of the metacrisis. It was always there, burning inside him and waiting until the right moment to break free… the ‘right moment’ that never came until it was too late.

She smiles faintly, just a small upturn of lips. Rose looks troubled still. “But… I love  _you_ , too,” she insists, placing her hand against the left of his chest for emphasis. “You know  _that_ , right?”

He locks eyes with her, hardly able to believe he’s this lucky. She understands, his brilliant, clever Rose. And not only that but she loves him, in all his divergent parts with all his flaws and inadequacies. It’s too much and he’s overcome with how much he loves this woman; how indebted he is to her and how badly he wants to make her happy for the rest of their lives.

After a moment, he sees the doubt filter into her stare and realizes she’s waiting for an answer.

“Yes,” he whispers softly.

She smiles, then, a true Rose Tyler grin and pulls him down for a kiss. Her mouth opens to him like it has a thousand times before, easily and with an appreciative moan. They haven’t really detangled, so she just sinks deeper into his embrace, pressing her body against him in pure feline desire. It still surprises him how quickly he can get lost in her, how soon she always has him up and ready.

“Dinner…” he offers weakly, a thin argument he doesn’t really support.

“Can wait…” she trails off between kisses.

She forgets to turn the stove off, and there is a small fire in the kitchen an hour later. But it’s worth it to hear her come apart in his arms with his name on her lips. To know without a doubt that Rose loves him, at any given point in time and space.

 

**Author's Note:**

> The real chemistry article that inspired Tentoo’s geeky t-shirt: http://www.rsc.org/chemistryworld/News/2008/October/23100802.asp


End file.
